Commercial transition metal sulfide (TMS) catalysts and enzymes containing TMS sites have caused researchers to focus attention on the coordination chemistry of sulfido-molybdenum complexes. Efforts to develop mononuclear, polynuclear, and heteronuclear Mo-S complexes which serve as structural or reactivity models for molybdenum-sulfido catalytic systems have led to the synthesis of several molybdenum complexes. However, efforts to produce these complexes are significantly restricted by the lack of appropriate Mo-S starting materials.
Hydrated salts containing Mo.sub.2 S.sub.12.sup.2- as an anion were first prepared as ammonium salts. A. Muller, W. Nolte, and B. Krebs, "[(S.sub.2).sub.2 Mo(S.sub.2).sub.2 Mo(S.sub.2).sub.2.sup. 2-, a Novel Complex Containing Only S.sub.2.sup.2 - Ligands and a Mo-Mo Bond", Angew. Chem. Int. Engl., Vol. 17, p. 279 (1978) discuss preparing Mo.sub.2 S.sub.12.sup.2- anion-containing salts. The method involves heating an ammonium sulfide solution with (NH.sub.4).sub.2 MoO.sub.4, separating the mixture, and cooling and diluting the filtrate. During the reaction, Mo.sub.3 S.sub.13.sup.2- anions are also formed. In addition, the synthesis led to variable yields of the desired ammonium salt, (NH.sub.4).sub.2 Mo.sub.2 S.sub.12.2H.sub.2 O. Salts containing the Mo.sub.2 S.sub.12.sup.-2 anion and a cation other than ammonium (NH.sub.4.sup.+) were unknown.
M. Draganjac, et al., "Synthesis, Interconversions and Structural Characterization of the [(S.sub.4).sub.2 Mo.sub.2 S.sub.10).sup.2-, (Mo.sub.2 S.sub.10).sup.2- and (Mo.sub.2 S.sub.12).sup.2- Anions", Inorg. Chem., Vol. 21, pp. 3321-3332 (1982) discuss the preparation of (Ph4P).sub.2 Mo.sub.2 S.sub.10.56, a mixture of (Ph.sub.4 P).sub.2 Mo.sub.2 S.sub.10 and (Ph.sub.4 P).sub.2 Mo.sub.2 S.sub.12, by reacting (Ph.sub.4 P).sub.2 MoS.sub.4 with dibenzyltrisulfide in dimethylformamide (DMF). Ethanol and ether were then added and dark red crystals resulted which were washed with ethanol and ether. A 58% yield of (Ph.sub.4 P).sub.2 Mo.sub.2 S.sub.10.56 was obtained.
S. A. Cohen, et al., "Dinuclear Tungsten (V) and Molybdenum (V) Compounds Containing M.sub.2 S.sub.2 (.mu.-S).sub.2.sup.2+ Cores: Synthesis and Reactivity of [N(C.sub.2 H.sub.5).sub.4 ].sub.2 M.sub.2 S.sub.12 (M=W or Mo) and the Crystal Structure of [N(C.sub.2 H.sub.5).sub.4 ].sub.2 W.sub.2 S.sub.2 (.mu.-S).sub.2 (S.sub.4).sub.2 ", Inorg. Chem., Vol. 24, p. 4657 (1985) teaches preparing salts containing Mo.sub.2 S.sub.12.sup.2- anions by reacting elemental sulfur and (NH.sub.4).sub.2 MoS.sub.4 in DMF and heating. A red-black solution is formed and tetraethylammonium bromide is then added and the DMF is removed at 65.degree. C. under vacuum. The solids are extracted with acetonitrile to form a filtrate and a salt containing an Mo.sub.2 S.sub.12.sup.2- anion is recrystallized from the filtrate. A 62% yield of the salt was obtained.
Although capable of producing compounds containing Mo.sub.2 S.sub.12.sup.2- anions, the reaction schemes in the prior art suffer from numerous drawbacks. These drawbacks include: low yields of Mo.sub.2 S.sub.12.sup.2- anion containing compounds; low Mo.sub.2 S.sub.12.sup.2- anion purity; the production of dimethylammonium bromide, a skin and mucous membrane irritant; the need to bubble H.sub.2 S gas into solution to produce Mo.sub.2 S.sub.12.sup.2- anions; and difficulty in controlling the concentration of the sulfide sulfur reactant. As a result, the prior art preparations are not suitable for large scale production of pure compounds containing the Mo.sub.2 S.sub.12.sup.2- anion.
It is therefore an object of the invention to provide a method for producing, in relatively high yield, molybdenum and sulfur containing compounds in pure form that have Mo.sub.2 S.sub.12.sup.2- as the anion.
Another object of the invention is to provide a method for producing molybdenum and sulfur containing compounds that have Mo.sub.2 S.sub.12.sup.2- as the anion that provides a means for controlling the sulfide sulfur concentration of the reaction.
Other objects of the invention will become more apparent to those skilled in the art upon reading the following description in conjunction with the examples, provided for illustrative purposes.